Introduction

RIO modules constitute a network junction. An RIO module joins ring traffic with RIO module traffic.

Each junction presents the queueing point, which can add delay — or jitter — to the system. If 2 packets simultaneously arrive at a junction, only 1 can be immediately transmitted. The other waits for a period referred to as “one delay time” before it is transmitted.

Because RIO packets are granted priority by the M580 network, the longest an RIO packet can wait at a junction is 1 delay time before it is transmitted by the module.

The following scenario depicts the ways in which a junction handles packets that arrive simultaneously.

RIO Module

In the following example, an RIO module originates packets for transmission and forwards packets it receives on the ring:

The RIO module handles RIO packets in the following sequence:

Time

Ring In

RIO Packet

Ring Out

Comment

T0

1 (started)

a

Packet “a” arrived after transmission of packet “1” begins.

T1

2

1

Packet “2” arrived after packet “a.”

T2

3

a

Packet “3” arrived after packet “2.”

T3

4

2

Packet “4” arrived after packet “3.”

T4

5

3

Packet “5” arrived after packet “4.”